Biological industries that produce chicken embryo allantoic fluid from eggs require drilling or punching holes on the top of the egg for inoculation, and cutting for removal of the top of the egg for harvesting the fluid or embryo. Traditionally, holes are drilled in the egg top by a mechanical method using a dental drill. The holes may also be punched by using stainless steel needles. The cuts are made by a thermal process which involves two steps: punch a hole on the egg top, and then place and rotate a propane torch burner over the end of the egg. During mechanical drilling and punching, the forces that act on the tool and on the egg may cause fracture of the egg if the process is not carefully controlled. In addition, the problem of sterility with the drill requires the application of antiseptic fluid. Thermal cutting with the propane torch causes strong heating of the eggshell, generates thermal stresses, and if not controlled properly, results in destruction of the egg. In fact, the rationale for punching a hole prior to propane torch cutting is to eliminate the stresses caused by gas pressure increase inside the egg due to the heating process. Both the mechanical and flame processes have several drawbacks including: sterility, long process time, poor cut quality and high scrap rate.
Those concerned with these and other problems recognize the need for an improved method for machining eggshells.